Respirating gas supply method and apparatus therefor

ABSTRACT

In various embodiments of a respirating gas supply method and apparatus a control circuit (32) responsive to a sensor (28) operates valve means (26) to supply pulses of respirating gas through a single hose cannula (48) to an in vivo respiratory system when negative pressure indicative of inspiration is sensed by the sensor (28). The control circuit (32) operates the valve (26) to communicate the in vivo respiratory system with a supply of gas (20) only if the negative pressure sensed by the sensor (28) does not occur within a predetermined yet selectively variable required minimum delay interval between successive pulsed applications of gas to the in vivo respiratory system. The pulse of gas applied to the in vivo respiratory system can be spiked pulses or square pulses. Humidifiers, nebulizers, and sources of a second gas are provided in accordance with various embodiments. Apnea event detection is also provided.

BACKGROUND

This invention pertains to apparatus and methods for providingsupplemental respirating gas, such as oxygen, to an in vivo respiratorysystem.

U.S. patent application Ser. No. 210,654, filed Nov. 26, 1980 now U.S.Pat. No. 4,414,982 by Gerald P. Durkan and commonly assigned herewith,is incorporated herein by reference as illustrating a method ofsupplying respirating gas wherein a pulse of gas is supplied to an invivo respiratory system substantially at the beginning of inspiration.U.S. patent application Ser. No. 210,654 also discloses a primarilyfluidically-operated apparatus comprising a demand gas circuit. Thefluidic apparatus comprising the demand gas circuit carries out themethod described above and, by virtue of the method, is significantlysmaller and more compact than other demand gas-type apparatus whichsupply respirating gas essentially throughout the duration ofinspiration. While this fluidic apparatus has proven extremely effectivein such products as home oxygen concentrators and oxygen dillusion ordelivery systems, for example, a further reduction in overall apparatussize would further enhance the utility of such products.

Many devices, including those depicted in U.S. patent application Ser.No. 210,654, are adapted to monitor or sense pressure direction in an invivo respiratory system throughout the respiratory cycle and toselectively supply gas in accordance with the pressure direction in thein vivo respiratory system. In this respect, the in vivo respiratorysystem creates a negative pressure when an attempt is made to inspireand create positive pressure when an attempt is made to exhale. Incertain instances it is advantageous to supply pulses of gas such asthese described in the application Ser. No. 210,654 but in such a mannerthat a pulse is not necessarily supplied for every detection of negativepressure in the in vivo respiratory system. For example, should the invivo respiratory system attempt to inspire too frequently, an apparatusoperating strictly in the manner described in U.S. patent applicationSer. No. 210,654 would in some instances cause the in vivo respiratorysystem to overoxygenate. While breathing rate control circuits andoverride circuits have been disclosed in the prior art (such as U.S.Pat. Nos. 4,206,754 to Cox and 4,141,754 to Ismach, for example) thesecircuits are incompatible with the device described in the referencedapplication.

U.S. patent application Ser. No. 210,654 also illustrates the usage of a"split" or "double hose" cannula which interfaces the in vivorespiration system through the nares with the sensing and gas supplyelements of the apparatus disclosed therein. Although the apparatusperforms superbly using the double hose cannula, employment of a singlehose cannula rather than a double hose cannula would enable both thesensing of the pressure direction in the in vivo respiratory system andthe delivery of respirating gas to the in vivo respiratory system to beaccomplished through the same hose. Single hose cannulae, being lessexpensive to manufacture and more convenient for the physician and user,are generally more prevalent on the market than double hose cannulae.Thus, it would be advantageous to adapt systems such as that disclosedin the referenced application for compatability with a single hosecannula.

Moreover, it is generally preferable to humidify respirating gas beforesupplying the gas to an in vivo respiration system. In somecircumstances it is desirable to nebulize the respirating gas withmedication before supplying the gas to the in vivo respiration system.Although humidifiers and nebulizers have long been used with oxygensupply systems, it is not evident from the prior art how a humidifier ornebulizer can be appropriately utilized with apparatus such as thosedescribed in U.S. patent application Ser. No. 210,654, especially ifapparatus of that type are used with a single hose cannula as discussedabove. A great danger in utilizing humidifiers and/or nebulizers witheither single or double hose cannula systems is the transfer of moisturethrough the hose leading to sensing means used to determine thedirection of pressure in the in vivo system. Moisture in the hoseleading to the sensing means contaminates the sensor and tends toconsiderably shorten the life of the sensor.

In some situations it may also be desirable to supply another gas, suchas an anesthetic gas, to in vivo respiratory system along with thesupply of respirating gas. In some situations, the dosage of second gasmust usually be in controlled relation to the amount of respirating gassupplied simultaneously therewith. Moreover, a serious problem resultsin a demand gas-type device when medicating gas is continually appliedregardless of the ability or inability of the in vivo system to demandthe respirating gas.

In view of the foregoing, it is an object of the present invention toprovide a demand respirating gas supply method and apparatus whichprevents overoxygenation by supplying a fixed volume dose of respiratinggas per unit time to an in vivo respiratory system.

An advantage of the invention is the provision of a demand respiratinggas supply method and apparatus which employs a single hose cannula,thereby allowing pressure sensing and gas supply to be accomplishedthrough the same line.

A further advantage of one embodiment of the invention is the provisionof a method and apparatus for supplying spiked shaped pulses of gas atthe beginning of an inspiration.

An advantage of another embodiment of the invention is the provision ofa method and apparatus for supplying square shaped pulses of gas at thebeginning of an inspiration.

Yet another advantage of the invention is the provision of a compactrespirating gas supply apparatus.

Still another advantage of the invention is the employment ofhumidifiers, nebulizers, and the like without deleterious impact upon asensor used in a respirating supply gas apparatus.

SUMMARY

In various embodiments of a respirating gas supply method and apparatus,a control circuit responsive to a sensor operates a valve to supplypulses of respirating gas through a single hose cannula to an in vivorespiratory system when negative pressure indicative of inspiration issensed by the sensor. The control circuit operates the valve tocommunicate the in vivo respiratory system with a supply of gas only ifthe negative pressure sensed by the sensor does not occur within apredetermined yet selectively variable required minimum delay intervalbetween successive pulsed application of the gas to the in vivorespiratory system.

In some embodiments, a three-way valve having ports connected to thesensor, the gas supply, and the single hose cannula is used. In anotherembodiment, a four-way valve facilitates usage of the apparatus inconjunction with a humidifier and/or a nebulizer.

In one embodiment a respirating gas supply apparatus has a sensorcomprising a biased fluidic amplifier and a pressure-to-electric (P/E)switch.

Apparatus according to the embodiments described herein can be operatedto supply spiked pulses or square pulses of gas depending on whether aflowmeter is connected between the supply of gas on the valve.

The control circuit of the respirating gas supply apparatus also hasmeans for determining if the in vivo respiratory system has failed todemand a pulse of gas after the elapse of a predetermined butselectively variable maximum time interval. Upon detecting such an apneaevent, the apparatus activates various indicator or alarm means andoperates the valve to supply an additional pulse or pulses of gas to thein vivo respiratory system.

Upon the detection of an appropriate apnea event, respirating gas supplyapparatus according to various embodiments supply stimulus to the upperairway passages of an in vivo respiratory system in an effort todislodge any occlusion or obstruction in the upper airway passages. Inone embodiment the stimulus applied is a high pressure pulse of gas. Inanother embodiment an electrical signal is applied to anelectromyographic electrode (279) positioned in proximity to a nervecontrolling a muscle or organ which may obstruct the upper airwaypassage.

BRIEF DESCRIPTION OF THE DRAWINGS

The foregoing and other objects, features and advantages of theinvention will be apparent from the following more particulardescription of the preferred embodiments of the invention, asillustrated in the accompanying drawings in which like referencecharacters refer to the same parts throughout different views. Thedrawings are not necessarily to scale, emphasis instead being placedupon illustrating the principles of the invention.

FIG. 1A is a schematic diagram showing a gas supply apparatus accordingto an embodiment of the invention wherein gas is supplied in a spikedpulse mode;

FIG. 1B is a schematic diagram showing a gas supply apparatus accordingto an embodiment of the invention wherein gas is supplied in a squarepulse mode;

FIG. 1C is a schematic diagram showing a gas supply apparatus accordingto an embodiment of the invention wherein sensing means comprises afluidic amplifier;

FIG. 2 is a schematic diagram showing a gas supply apparatus accordingto an embodiment of the invention wherein supply gas is humidified;

FIG. 3 is a schematic diagram showing a gas supply apparatus accordingto another embodiment of the invention wherein supply gas is humidified;

FIG. 4A is a graph illustrating a spiked pulse method of supplying gasaccording to a mode of the invention;

FIG. 4B is a graph illustrating a square pulse method of supplying gasaccording to a mode of the invention;

FIG. 5 is a schematic diagram showing a control means according to anembodiment of the invention;

FIG. 6 is a schematic diagram showing a gas supply apparatus accordingto another embodiment of the invention wherein a second gas is alsosupplied;

FIG. 7A is a plan view of a fluid amplifier of the embodiment of the gassupply apparatus of FIG. 1C;

FIG. 7B is a graph illustrating the output pressure gain curve for thefluidic amplifier shown in FIG. 7A; and,

FIGS. 8A, 8B, and 8C are schematic diagrams showing differingembodiments of gas supply apparatus which detect apnea events andattempt to remedy apnea events caused by occlusion of upper airwaypassages in the in vivo respiratory system.

DETAILED DESCRIPTION OF THE DRAWINGS

The respirating gas supply system of the embodiment of FIG. 1A comprisesa source of gas 20; a flowmeter 22; a fluidic capacitance 24; valvemeans 26; sensing means 28; and, control means 32.

Source 20 is typically a source of oxygen gas. Depending upon theparticular environment of use, source 20 may be a portable tank or awall supply, for example. Source 20 is connected by line 34 to theflowmeter 22. As used herein unless otherwise indicated, any fluidconveying means, such as a duct, pipe, channel, or other closed fluidconduit, is referred to as a line.

While the flowmeter 22 may be of any conventional type, a ballfloat-type flowmeter manufactured by Dwyer is suggested as oneacceptable model. The flowmeter illustrated in FIG. 1A comprises aneedle valve (not shown) which has an inherent resistance FR to the flowof gas. The flowmeter inherent resistance is dependent, inter alia, onthe dimensions of the needle valve and the needle orifice. The flowmeter22 is connected to the capacitance by line 40.

Capacitance 24 is shown as a tank but in another embodiment is merely arelatively long length of tubing. As seen hereinafter, the volume ofcapacitance 24, the flowmeter inherent resistance FR, the inherentresistance VR of the valve 26, and the interrelationship between thesefactors influence the amplitude of a pulse of gas produced by therespirating gas supply system of FIG. 1A.

The valve means 26 of the embodiment of FIG. 1A is a three-way twoposition solenoid-actuated spool valve having ports 26a, 26b, and 26c inits bore. Port 26a is connected by line 46 (a single hose) to a means 48for supplying gas to an in vivo respiratory system. Although theparticular means shown in FIG. 1A is a single hose cannula, it should beunderstood that other suitable devices, such as an endotracheal tube ora hand resuscitator, for example, may be employed. The aforesaid line 40ultimately connects ports 26b to the source 20. Port 26c is connected byline 50 to the sensing means 28.

As shown in the FIG. 1 representation of the valve 26, the spool ofvalve 26 is biased to its first position to connect port 26a to port 26cso that the cannula 48 (and hence in vivo respiratory system (not shown)including nares in which the cannula 48 is inserted) is in fluidiccommunication with the sensing means 28. It should be understood thatthe valve 26 can be operated to move the spool to its second position toconnect port 26a with port 26b so that a pulse of gas is supplied to thein vivo respiratory system through the single hose 46. When connected inthis manner, the valve 26 has an inherent resistance VR to the flow ofgas which is dependent on the size of the orifice connecting port 26a toport 26b.

The valve 26 is electrically controlled by control means 32 in themanner hereinafter described. While the valve 26 shown in FIG. 1A is ofa type manufactured by Lee as model LFAA 1200318H, any comparable modelcan be used.

The sensing means 28 of FIG. 1 comprises suitable means for sensing anegative fluidic pressure applied along line 50 and for generating anelectrical signal in accordance with the sensing of the negative fluidicpressure. In one embodiment the sensor 28 comprises apressure-to-electric (P/E) switch, such as a Model E P/E Switchmanufactured by the Dietz Company which can sense pressures as low as0.02 inches (column of water). In this embodiment, the negative inputport of the P/E switch is connected to the line 50 while the positiveinput port is left open to ambient. Large diaphragms used instate-of-the-art P/E switch technology, such as the two inch diameterdiaphragm of the Dietz Model E P/E, have considerable internal volumeand hence, for some environments of use, a significantly long timeresponse. Many P/E switches must also be mounted horizontally to achievemaximum sensitivity, but mounting the switches horizontally presentsanother problem--acceleration sensitivity of the diaphragm.

The sensing means 28C of FIG. 1C comprises means 29 for sensing positivefluidic pressure and for generating an electrical signal in accordancewith the sensed fluidic pressure, as well as amplification means such asfluid amplifier 30. The fluid amplifier 30 depicted in FIG. 1C is abiased turbulent proportional amplifier shown in more detail in FIG. 7A.

The biased fluidic amplifier 30 has a power input stream 30; two controlports 30b and 30c; and, two output ports 30d and 30e. The power streaminput port 30a is connected by the line 44 ultimately to the source 20.A variable restrictor 52 on line 44 is used to limit the magnitude offlow and pressure of flow of the input stream and thus the sensitivityof the fluidic amplifier 30. Control port 30b is connected by line 50 toport 26c of the valve 26 such that negative pressure in line 50 (createdby inspiration in the in vivo respiratory system) deflects the powerstream to output port 30d. The amplifier 30 is biased such thatnon-negative pressure in line 50 results in the power stream passingthrough the output port 30e.

The amplifier structure of FIG. 7A illustrates the biased nature of theamplifier 30. The amplifier 30 is configured with an off-set splitter.That is, the power input stream 30a is canted so that, absent controlsignals at ports 30b (also labeled C_(r)) and 30c (C_(l)), the output isnormally biased to the left output port 30e (L). When negative pressureis applied through port 30b, the output switches to port 30d. When thenegative pressure ceases, the output automatically switches back to port30e. In a preferred embodiment the amplifier 30 operates with a lowpower supply so that the jet is laminar. The output pressure gain curvefor the fluid amplifier 30 of FIG. 7A is shown in FIG. 7B.

A fluidic amplifier of the type manufactured by TriTec, Inc. as ModelNo. AW12* functions well as the amplifier 30 of FIG. 7A to give asensitivity to negative pressures at least as low as 0.02 cm water. Itshould be understood by those skilled in the art that other fluidicelements, such as a NOR gate, can be configured with the circuitry shownto yield acceptable results.

In the embodiment of FIG. 1C a pressure-to-electric (P/E) switch 31 isused as the means for sensing positive pressure and for generating anelectrical signal in accordance with the sensed fluidic pressure. TheP/E switch 31 illustrated in FIG. 1C is a conventional P/E switch suchas that manufactured by Fairchild as Model PSF 100A. The positive inputport of the P/E switch 31 is connected to the output port 30d of sensor30 by line 54 while the negative input port thereof is open to ambient.For the particular sensing means 28 illustrated in FIG. 1C, the P/Eswitch 31 should be sensitive enough to switch when positive pressure aslow as 0.02 cm. of water is incident thereon. When P/E switch 31receives such pressure, P/E switch 31 closes a switch 36 as seenhereinafter with reference to FIG. 5.

Referring now again to the embodiment of FIG. 1A, it should beunderstood that other types of sensing means 28 may be employed. Thoseskilled in the art recognize that (if operating requirements permit) athermistor system can be utilized, provided the thermistor system ismade direction sensitive (by utilizing two thermistors and appropriatetime delay measurement circuitry). Ordinarily, however, the flowtype (asopposed to pressure-type) sensitivity of a thermistor prevents thethermistor from sensing flow rapidly enough to facilitate the supply ofan oxygen pulse early in inspiration, such as in the manner taught inU.S. patent application Ser. No. 210,654. In another embodiment, apressure transducer functions as the sensing means 28. The pressuretransducer can be a solid state, a capacitance, or an electromechanical(diaphragm-type) transducer, depending on the sensitivity required.Transducers provide an analog signal and require rather complexelectrical circuitry. A suitable solid state crystal may someday bedeveloped to function as the sensing means 28 in accordance with desiredsensitivity requirements.

The respirating gas supply system of FIG. 1B resembles the system ofFIG. 1A but does not have the flowmeter 22. As seen hereinafter, thesystem of FIG. 1A produces a spiked pulse of gas whereas the system ofFIG. 1B produces a square pulse of gas.

The respirating gas supply system of the embodiment of FIG. 2 basicallyresembles the system of FIG. 1B but, rather than employ a three-wayvalve, utilizes a four-way two-position valve 58 as its valve means. Thefour-way valve 58 has four ports in its bore: port 58a connected by theline 46 to the cannula 48; port 58b connected by line 42 ultimately tothe source 20; port 58c connected by line 50 to control port 30b ofsensor 28; and, port 58d connected by a line 60 to an input of ahumidifier 62. Valve 58 can be any conventional four-way two positionvalve, such as the solenoid-actuated spool valve model 8345E1manufactured by ASCO. As shown in the FIG. 2 representation of valve 58,the valve 58 is biased in a first position to connect port 58a to port58c so that cannula 48 (and hence the in vivo respiratory system) is influidic communication with the sensor 28. It should be understood thatthe valve 58 can be actuated to a second position to connect port 58b toport 58d. When this occurs, gas is supplied through the valve 58 andline 60 to the input of humidifier 62.

Humidifier 62 is a bubble type humidifier, such as the model 003-01humidifier available from Respiratory Care, Inc. Humidifier 62 yields ahumidified gas flow on line 64 connected to the output of the humidifier62. Line 64 connects with a line 46 at point 66. A variable resistance64R on line 64 insures that upon inspiration the path of leastresistance is through line 46 and the value 58 rather than through line46.

It should be understood that the apparatus of the embodiment of FIG. 2can be connected in the manner of FIG. 1A (that is, with a flowmeter) tooperate in a spiked pulse mode rather than a square pulse mode.

The respirating gas supply system of the embodiment of FIG. 3 basicallyresembles the system of FIG. 1B but further incorporates the humidifier62. A line 65 connects to line 46 at point 67. The line 65 connects thepoint 67 to the input of the humidifier 62. Line 64 from the output ofthe humidifier 62 terminates in a nozzle 68 of a venturi 70. The venturi70 is connected on line 46 intermediate the port 26a of valve 26 and thecannula 48. A variable resistance 65R on line 65 insures that uponinspiration the path of least resistance is through the line 46 and thevalve 26 rather than through line 65. Resistance 65R also serves tocontrol the flow into the humidifier 62 through line 65. The venturi 70shown is a type F-4417-10 available from Airlogic, although anycomparable venturi is suitable. Again, it should be understood that theembodiment of FIG. 3 can, if desired, incorporate a flowmeter in orderto operate in a spiked pulse mode.

It should be understood by those skilled in the art that a device foradministering medication, such as a nebulizer, can be connected in thesystems of FIGS. 2 or 3 in essentially the same respective manners asthe humidifier 62 shown therein.

The respirating gas supply apparatus of the embodiment of FIG. 6basically resembles the embodiment of FIG. 1B but further includes meansfor suppling a second gas to the in vivo respiratory system. Theapparatus of FIG. 6 further comprises a source 120 of a second gas (suchas an anesthetic gas, for example), a capacitance 124; and, second valvemeans 126. Source 120 is connected to capacitance 124 by line 134;capacitance 124 is connected to the valve means 126 by line 142. Theapparatus of the embodiment of FIG. 6 can be used, if desired, with ahumidifier in the manner described above with reference to either FIG. 2or FIG. 3.

Valve 126 is a two-way two position solenoid-actuated spool valve havingport 126a and 126b in its bore. The central spool of valve 126 is biasedin a first position as shown in FIG. 6 so that ports 126a and 126b arenot communicating. Port 126b of valve 126 is connected by line 144 to apoint 146 where line 144 joins line 46. A variable resistance 147 online 144 insures that upon inspiration the path of least resistance isthrough the line 46 and valve 26 rather than through line 144. Thesolenoid valve 126 is electrically connected by lines L3' and L3 to thecontrol means 32. In other embodiments the solenoid valve ismechanically connected to a control means.

The control means 32 of the embodiment of FIG. 5 is suitable for usewith apparatus constructed in accordance with any of the foregoingembodiments. Control means 32 is a circuit comprising four NAND gates(72, 74, 76, and 78); four NOR gates (80, 82, 84, and 86); threetransistors (T1, T2, and T3); a 555 timer chip 88; a 556 dual timer chip90; LEDs 92 and 94; piezo electric member 96; and, various resistancesand capacitances as hereinafter designated.

As used with reference to FIG. 5, the notation "LX" denotes anelectrical line (as opposed to a fluidic line) where X is an appropriatereference number. For example, controller 32 includes a line L1connected to a high DC voltage supply (not shown) and line L2 connectedto a low DC voltage supply (also not shown). The potential differenceacross L1 and L2 is between 12 and 15 volts DC.

The 556 dual timer chip 90 shown in FIG. 5 is a 14 pin chip manufacturedby National Semiconductor as part number LM 556CN. It should beunderstood that any comparable 556 dual timer chip is suitable for thecircuit of FIG. 5. For the particular chip shown, pins 1-7 correspond topins of a first timer in the dual timer while pins 8-14 correspond topins of a second timer. The pins are labeled as follows:

PIN DESCRIPTION FOR 556 CHIP

    ______________________________________                                        DESCRIPTION     TIMER 1   TIMER 2                                             ______________________________________                                        discharge       1         13                                                  threshold       2         12                                                  control voltage 3         11                                                  reset           4         10                                                  output          5          9                                                  trigger         6          8                                                  ground          7                                                             operating voltage         14                                                  ______________________________________                                    

The pin connections for the first timer of the 556 dual timer 90 are asfollows: Pins 1 and 2 are connected to line L2 through a seriescombination of resistor R1 and a 100K variable potential resistance R2.Pins 1 and 2 are also connected to line L2 through capacitance C1. Pin 3is connected to line L2 through capacitor C2. Pin 4 is connecteddirectly to line L1. Pin 5 is connected to the base of transistor T1through resistor R3. Pin 5 is also connected to the anode of LED 92 (thecathode of LED 92 being connected through resistor R4 to the line L2).Pin 6 is connected through capacitor C3 to the output terminal of NOR80. Pin 6 is also connected to line L1 through the resistor R14 and toline L2 through the resistor R15. Pin 7 is connected directly to lineL2.

The pin connections for the second timer of the 556 dual timer 90 are asfollows: Pin 8 is connected through capacitor C4 to the output terminalof NOR 84, as well as to line L1 through the resistor R16 and to line L2through the resistor R17. Pin 9 is connected to both input terminals ofNAND 74. Pin 10 is connected directly to line L1 and to a point 102discussed hereinafter. Pin 11 is connected through capacitance C5 toline L2. Pins 12 and 13 are connected to line L1 through a seriescombination of resistor R5 and a 100K variable potential resistor R6.Pins 12 and 13 are also connected to line L2 through capacitance C6. Pin14 is connected directly to line L1.

The 555 timer chip 88 shown in FIG. 5 is an eight pin chip manufacturedby National Semiconductor as part number LM 555CN. It should beunderstood that any comparable 555 chip is suitable for the circuitry ofFIG. 5. For the particular chip shown the pins are labeled as follows:

    ______________________________________                                        DESCRIPTION      PIN                                                          ______________________________________                                        ground           1                                                            trigger          2                                                            output           3                                                            reset            4                                                            control          5                                                            threshold        6                                                            discharge        7                                                            operating voltage                                                                              8                                                            ______________________________________                                    

The pin connections for the 555 timer chip 88 are as follows: Pin 1 isconnected directly to line L2. Pin 2 is connected to the output of NOR82 and to the base of transistor T2. Pin 3 is connected to both inputsof NOR 86 and to a point 98. Pin 4 is directly connected to line L1. Pin5 is connected to line L2 through capacitor C7. Pins 6 and 7 areconnected to line L2 through capacitance C8. Pins 6 and 7 are alsoconnected to line L1 through a series combination of resistances, thecombination including a resistor R7 and anyone of a group ofparallel-arranged resistances such as resistances Ra, Rb, and Rc . . . .Which of the parallel-arranged resistances is used depends on the manualpositioning of a switch 100 as described hereinafter. Pins 6 and 7 arealso connected to the emitter of transistor T2. Pin 8 is connecteddirectly to the line L1.

NAND 72 has a first input terminal 72a connected to line L1 throughresistance R8 and connected to L2 through the switch 36. A second inputterminal 72b of the NAND 72 is connected to the output terminal of NAND74. The output terminal of NAND 72 is connected to a first inputterminal 80a of NOR 80, as well as to both input terminals of thefollowing: NOR 82, NOR 84, and NAND 76. The first input terminal 80a ofNOR 80 is also connected to a point 104 intermediate the output terminalof NOR 86 and the anode of LED 94. The second input terminal 80b of NOR80 is connected to line L2 through resistor R9. The lines L4, L5, L6,and L7 shown in FIG. 5 are connected to further devices, such asinstrumentation which, unless otherwise noted herein, do not form partof the present invention.

Transistor T1 is a NPN transistor, such as the type available from GE aspart GE-66A. The emitter of transistor T1 is connected directly to lineL2. The collector of transistor T1 is isolated from line L2 by a diodeD1 (IN 4005) and is connected to the positive terminal of appropriatevalve means (such as valve 26 or valve 58) by line L3. Line L8 isconnected to the negative (or ground) terminal of the appropriate valvemeans.

Transistor T2 is a PNP transistor, such as the type available from GE aspart GE-65. The emitter of transistor T2 is connected to pins 6 and 7 oftimer 88. The base of transistor T2 is connected to the output of theNOR 82. The collector of the transistor T2 is directly connected to lineL2.

FIG. 5 also includes an alarm circuit generally denoted as 100. A point102 of alarm circuits 100 is connected both to line L1 and (throughcapacitor C9) to line L2. Terminal 96b of the piezo electric 96 isconnected to point 102 through resistance R10 and to the base oftransistor T3 through resistor R11. Terminal 96a of the piezo 96 isconnected to point 102 through resistance R12. Terminal 96c of the piezoelectric 96 is connected to point 98 and to the emitter of transistorT3. The alarm circuit 100, when activated, functions as an oscillatorand drives therefor to produce audible oscillation. It should beunderstood that any conventional circuit, including buzzers andelectromechanical alarms, may be utilized instead.

Transistor T3 is a NPN transistor, such as the type available from GE aspart GE-66A. The collector of transistor T3 is connected throughresistor R12 to the point 102. The other connections of the transistorT3 are described above.

The NOR gate 86 has its output terminal connected to the anode of theLED 94. The cathode of the LED 94 is connected through resistor 13 tothe line L2.

Conventional NOR gates can be used for the NORs 80, 82, 84 and 86 andconventional NAND gates can be used for the NANDS 72, 74, 76 and 78utilized in the controller of FIG. 5. For the embodiment of FIG. 5,however, the NANDs illustrated are parts 4011 manufactured by NationalSemiconductor and the NORs are parts 4001B manufactured by NationalSemiconductor.

The suggested values for the resistances and capacitances for theembodiment of FIG. 5 are as follows:

    ______________________________________                                        RESISTANCES            CAPACITANCES                                           ______________________________________                                        R1 =      10K          C1 =     10μ                                        R2 =      (variable)   C2 =     0.02μ                                      R3 =      1K           C3 =     0.1μ                                       R4 =      2K           C4 =     0.1μ                                       R5 =      10K          C5 =     0.02μ                                      R6 =      (variable)   C6 =     22μ                                        R7 =      1.2K         C7 =     0.02μ                                      R8 =      2K           C8 =     220μ                                       R9 =      20K          C9 =     10μ                                        R10 =     220K                                                                R11 =     10K                                                                 R12 =     510K                                                                R13 =     2K                                                                  R14 =     1 M                                                                 R15 =     1 M                                                                 R16 =     1 M                                                                 R17 =     1 M                                                                 ______________________________________                                    

In the operation of the respirating gas supply system of the embodimentof FIG. 1A, gas from the source 20 is passed through line 34 to theflowmeter 22. The needle valve (not shown) in flowmeter 22 is set tocontrol the rate of flow through the flowmeter 22. Gas flowing throughthe flowmeter 22 continues through line 36 to the capacitance 24. Fromcapacitance 24 the gas passes into line 42. The gas in line 42 does notpass through the valve 26 until the valve 26 is actuated so that port26b thereof is connected to port 26a in the manner hereinafterdescribed.

The cannula 48 is inserted in the nares of an in vivo respiratorysystem. When a negative pressure is created by an attempted inspirationby the in vivo respiratory system, the negative pressure is applied tothe single hose 46.

For the apparatus shown in the embodiment of FIG. 1A, valve 26 isnormally in the position shown in FIG. 1A with port 26a connected toport 26c. Upon inspiration a negative pressure is created in line 50. Inthe embodiment described above wherein sensor 28 is a P/E switch, forexample, the negative pressure in line 50 acts upon the negativepressure input port of the P/E switch. The P/E switch accordingly closesthe switch 36 of FIG. 5.

For the apparatus shown in the embodiment of FIG. 1C, the negativepressure in line 50 created by inspiration is applied to the controlport 30b of fluidic amplifier 30. The negative pressure at control port30b causes the power stream input of amplifier 30 to be deflected sothat output occurs at the output port 30d rather than at the output port30e to which it is normally biased. The output from port 30d creates apositive fluid signal on line 54 which is applied to the positive inputport P/E switch 31. The P/E switch 31 accordingly closes the switch 36of FIG. 5.

With respect to the controller 32 as depicted in FIG. 5, the closing ofswitch 36 completes a circuit between lines L1 and L2 and causes a falsesignal to be applied to input port 72a of NAND 72. Since the input port72b normally receives a true signal (except when the negative pressureis sensed during a required minimum delay interval after the nextpreceeding application of gas in the manner hereinafter described), theoutput of NAND 72 is true. Accordingly, input terminal 80a of NOR gate80 goes true. Likewise, all input terminals of NAND 76, NOR 82, and NOR84 are true.

Unless an apnea event is detected as hereinafter described, or unless atrue signal is received on line L4, the input terminal 80b is false. Atthis point, the output of NOR gate 80 is false. The output of NOR 84 isalso false.

False outputs from the NOR gates 80 and 84 are applied to pins 6 and 8of the dual timer 90. Pin 6 is the trigger input of the first timerincluded in the dual timer 90; pin 8 is the trigger input of the secondtimer included in the dual timer 90. As result of trigger pins 6 and 8going from true to false, the outputs from corresponding pins 5 and 9 gotrue.

Output pin 5 of the dual timer 90 going true causes transistor T1 toconduct, so that a current is established on line L3. The resultantelectrical signal on line L3 causes the solenoid valve 26 to move fromits normally biased position as shown in FIG. 1A to its second positionwhere port 26b thereof is connected to port 26a.

Connecting port 26b of the solenoid valve 26 to port 26a enables the gasin line 42 to be transmitted through the valve 26. It should be recalledthat both the flowmeter 22 and the valve 26 have inherent resistances tothe flow of gas. The resistance FR of the flowmeter is generally greaterthan the resistance VR of the valve 26. Thus, as the valve 26 moves toconnect port 26a to ports 26b, pressure in line 42 drops and, if thevalve 26 remains in this position long enough, the rate of flow of thegas eventually is dictated by the resistance FR of the flowmeter 22.

Valve 26 thus allows a pulse of gas to pass from line 42 through valve26, through line 46 and cannula 48, and into the in vivo respiratorysystem. As seen hereinafter, the duration of the pulse is determined bythe length of the time the valve 26 remains in the position wherein port26b is connected to port 26a. The amplitude of the pulse is a functionof the flow rate through the valve 26. Incorporation of the flowmeter 22and to the fluid supply circuit of FIG. 1A causes the pulse of gasproduced to have a spike shape such as that shown in FIG. 4A. While thepulse of gases is being supplied, the LED 92 conducts to provide avisual indication of the same since the signal applied to transistor T1is also applied to the LED 92 anode.

When the output pin 5 of the dual timer 90 goes false the pulse of gassupplied through the valve 26 is caused to terminate. In this respect, afalse signal from pin 5 stops the transistor T1 from conducting, so thatthe signal on line L3 goes false. A false signal on line L3 causes thesolenoid valve 26 to return to its normally biased position as shown inFIG. 1A.

The time at which the output pin 5 of dual timer 90 goes false dependson the voltage value supplied to pin 2 of the dual timer 90. The voltagevalue at pin 2 of the dual timer 90 is dependent on the value chosen forthe 100K variable potential resistor R2. In this respect, the pulse ofgas is supplied until the voltage at pin 2 becomes two-thirds of thevoltage difference seen across pins 7 and 14. For the embodimentdescribed herein with reference to the circuit values mentioned above,when the resistance value of resistor R2 is 35K, for example, a pulse of0.5 seconds duration will be supplied.

As mentioned above, both timers in the dual timer 90 were triggered sothat the output pins 5 and 9 became true. A true signal on pin 5 movedthe solenoid valve 26 as described hereinbefore. A true on pin 9,however, causes the NAND gate 74 to go false, so that a false signal issupplied to the input terminal 72b of NAND 72. The output of NAND 72thus goes true and remains true as long as pin 9 of the dual timer 90 istrue.

While the output of NAND 72 remains true, pin 6 of the dual timer 90cannot be triggered false. In this respect, pin 6 of the dual timer 90remains false and cannot transition from true to false while pin 9 istrue. This means that should the in vivo respiratory system attempt toinspire while pin 9 of dual timer 90 is still true, the attemptedinspiration will have no effect on pin 6 of the dual timer 90, and henceno effect on the valve 26 so that an additional pulse of gas is notsupplied. Further attempted inspirations are ineffectual until theoutput pin 9 of dual timer 90 goes false. The time at which the outputpin 9 of dual timer goes false is selectively variable by the valuechosen for the 100K potential variable resistor R6. R6 affects thevoltage value applied to the threshold pin 12 of the dual timer 90,which determines when the output pin 9 goes false.

The value chosen for the resistor R6 determines a required minimuminterval between successive applications of gas to the in vivorespiratory system. This enables the apparatus to supply a fixed volumedose of respirating gas to the in vivo respiratory system per unit time.For the suggested circuit values given hereinbefore, resistor R6 chosento have a value of 73K gives a delay interval of 2.0 seconds. That is,when a negative pressure is sensed in the in vivo respiratory system,controller 32 will not permit a pulse of gas to be applied to the invivo respiratory system unless the required delay interval has elapsedsince the sensing of negative pressure which resulted in the nextpreceding application of gas to the in vivo respiratory system. In thismanner, the in vivo respiratory system is protected from overoxygenation should the in vivo respiratory system attempt an abnormallytrue number of inspirations. Without this protection feature, the invivo respiratory system would dangerously be supplied excess pulses ofgas when attempted inspirations are too frequent.

The foregoing method of requiring the elapse of a minimum delay intervalbetween successive applications of gas to the in vivo respiratory systemalso enables the apparatus of the embodiment discussed herein to beoperated when desired in accordance with the method described in U.S.patent application Ser. No. 210,654, already incorporated herein byreference. The pulse has a duration which can be less than the durationof the inspiration.

When the apparatus of the embodiment of FIG. 1A, for example, isoperated in accordance with a mode of the method of patent applicationSer. No. 210,654, the valve 26 returns to its normally biased positionwith port 26a connected to port 26c long before the negative pressure inthe in vivo respiratory system has ceased. In this respect, the pulse ofgas is supplied for a time period which is a fraction of the duration ofinspiration. Without the protective function of the second timer (andthe effect of output pin 9 of the dual timer 90 on NAND 80 to preventtrigger pin 6 of the dual timer 90 from going from true to false), anadditional pulse of gas would be supplied for the same inspiration.Thus, the protective function provided by the second timer of the dualtimer 90 of controller 32 allows the valve 26 to return to its normallybiased position and provides a buffer time interval in which the valve26 cannot again be actuated. Thus, controller 32 facilitates the usageof a single simple valve rather than a series of valves. Moreover,controller 32 and the valve means associated therewith facilitates theuse of a single hose 46 leading to a single hose cannula 48, whichallows both negative pressure and positive pressure to be transmittedthrough the same line 46.

The operation of the embodiment of FIG. 1B basically resembles that ofthe embodiment of FIG. 1A, but, rather than supplying a spiked pulse,the embodiment of FIG. 1B supplies a square pulse such as that shown inFIG. 4B. The square pulse results from the fact that there is noflowmeter in the line connecting the source 20 the the valve 26. Thus,the pressure in the capacitance 24--whether it be merely a length oftubing or a tubing and a tank--is the pressure of the source 22 ratherthan the pressure determined by the inherent resistance of theflowmeter. Thus, when valve 26 is opened to connect port 26a and port26b, the only limiting influence on the flow of gas is the inherentresistance of the valve 26. Without the inherent resistance FR of theflowmeter to dampen the pulse, the pulse assumes a square shape. It iscurrently thought that the square shape mode allows a more accuratedosage of volume flow to the cannula 48.

The operation of the embodiment of FIG. 2 also basis resembles that ofFIG. 1A but further supplies a humidified pulse of gas to the in vivorespiratory system. In the same manner described with reference to theFIG. 1A embodiment, controller 32 causes valve 58 to move to a positionwhere a port 58b communicates with port 58d when an appropriate negativepressure is detected in the in vivo respiratory system. A pulse of gasthen passes through line 60 to humidifier 62. A humidified pulse of gasleaves humidifier 62 and travels to the in vivo respiratory system online 64 and 46. In this manner moisture provided by the humidifiers 62does not contaminate ports 58a and 58c of valve 58, nor the sensor 28connected thereto by line 50.

It should be apparent by the operation of the embodiment of FIG. 1A thatthe operation of the embodiment of FIG. 3 is substantially the sameexcept that in the FIG. 3 embodiment the pulse of gas is also humidifiedby humidifier 62 before it passes to the in vivo respiratory system. Thepulse of gas leaves the valve 26 through line 46. A point 67 the pulsedivides so that a pulse first portion continues to travel on line 46 tothe input of verturi 70 and a pulse second portion is supplied on line65 to the input of the humidifier 62. The resulting humidified gas fromthe humidifier 62 is applied on line 64 to nozzle 68 of the venturi 70.The pulse of gas leaving venturi 70 is thus humidified for applicationto cannula 48. Use of venturi 70 in this manner eliminates the need ofadditional or more complicated valving means and protects the humidifier62 from higher pressures it might otherwise receive.

With respect to the embodiment of FIG. 6, a true signal on line L3causes not only the valve 26 to allow the passage of a pulse of a firstgas therethrough, but also causes the valve 126 to be actuated toconnect the source 120 of the second gas to the cannula 48. In thisrespect, the true signal on lines L3 and L3' cause valve 126 to beactuated so that port 126a is communicable with port 126b. A pulse ofsecond gas is thereby supplied through lines 144 and 46 to the cannula48.

The duration of the pulse of the second gas is determined in the samemanner as the duration of the pulse of the first gas. The amplitude ofthe pulse of the second gas is determined in much the same manner as theamplitude of the first gas, being dependent on the inherent resistanceVR of the valve 126 and the pressure of the source 120. It should beunderstood that, if desired, the apparatus of FIG. 6 can operate in thespiked pulse mode by connecting a flowmeter between valve 126 and source120.

The system of FIG. 6 provides the same protective features for the invivo respiratory system as do any of the foregoing embodiments.Additionally, the second gas (such as an anesthetic), is supplied onlywhen the first gas (such as oxygen) is also being supplied.

It has been described above how the controller 32 protects the in vivorespiratory system from overoxygenation should the in vivo respiratorysytem attempt an abnormally high number of inspirations. The followingdiscussion illustrates how the controller 32 indicates that the in vivorespiratory system is failing to attempt a further inspiration within amaximum time interval.

As mentioned above, when an inspiration (negative pressure from the invivo respiratory system) is sensed, both input terminals of NOR 82 aretrue. The resultant false output of NOR 82 is applied to input pin 2 ofthe timer 88, as well as to the base of transistor T2. Transistor T2,being a PNP type, conducts to discharge capacitor C8. The transitionfrom a true to a false input on pin 2 of timer 88 results in a trueoutput on pin 3 of timer 88. The true output signal from pin 3 isapplied to alarm circuit 100 so that the piezo element 96 thereinremains inactive. Likewise, the true output signal from pin 3 is appliedto both input terminals of NOR 86, resulting in a false output signalfrom NOR 86 at point 104. The false output from NOR 86 does not triggerthe LED 94 nor does it affect input terminal 80b of NOR 80.

When negative pressure is not sensed in the in vivo respiratory system,the output signal from NAND 72 is false. This false output signal,applied to both input terminals of NOR 82, results in a true output fromNOR 82. The true output signal from NOR 82 is applied to the base oftransistor T2, causing T2 to stop conducting. Pin 2 of timer 88 isprevented from triggering. As transistor T2 stops conducting, capacitorC8 charges up. When capacitor C8 charges up to the threshold level ofpin 6 of timer 88, the output pin 3 of timer 88 goes false. A falseoutput on pin 3 of timer 88 energizes the alarm circuit 100 so that anaudible signal is produced by the piezo element 96 in a conventionalmanner. Falso signals applied to both input terminals of NOR 86 resultin a true output signal at point 104. The true signal at point 104energizes the LED 94 to indicate an apneic event.

The true signal at point 104 is also applied to the input terminal 80bof NOR 80. Since the output signal of NAND 72 applied to terminal 80a ofNOR 80 is false, the output terminal of NOR 80 goes false. Thetransition from true to false at pin 6 of the timer 90 causes a pulse ofgas to be supplied to the in vivo respiratory system in the mannerdescribed above. If no further attempted inspiration is sensed,sequential pulses of gas are supplied in the same manner.

From the foregoing it should be apparent that a timer 90 provides amaximum time interval, and that the in vivo respiratory system mustattempt a further inspiration before the expiration of the maximum timeinterval. If the maximum time interval is exceeded by the lapse of timefrom a next preceeding application of a pulse of gas to a sensing ofnegative pressure, the timer 88 functions to activate both the audiblealarm of circuit 100 and the visible alarm of LED 94, as well as totrigger timer 90 so that a further pulse of gas is provided. Theduration of the maximum time interval depends on the particular valve ofthe resistance Ra, Rb, Rc, . . . manually chosen by the switch 100. Thisresistance valve determining the rate at which capacitor C8 charges,which in turn determines the time at which the threshold voltage appliedto pin 6 of the timer 88 is sufficiently high for the output state ofpin 3 thereof to change.

The apparatus of the embodiment of FIG. 8A somewhat resembles theapparatus of the embodiment of FIG. 1C, but the apparatus of FIG. 8 hasits sensor 28C' adapted for compatibility with an apnea detection andocclusion prevention (ADOP) circuit 200. The ADOP circuit 200 is apredominately fluidically operated circuit comprising a first fluidictiming circuit 202; a fluidic NOR gate 204; a second fluidic timingcircuit 206; and, valve means 208.

The sensor circuit 28C' resembles the circuit 28 of FIG. 5 with twoexceptions: (1) point 104 intermediate LED 94 and NOR 86 is not tied tothe input terminal 80b of NOR 80, and (2) the output port 30c of fluidicamplifier 30 is connected by a line 210 to a point 212 in the firsttiming circuit 202.

Point 212 of the timing circuit 202 is connected by parallel lines 214and 216 to a point 218. Intermediate points 218 and 212, line 214 has afluid resistance 220 thereon while line 216 has an exhaust means, suchas a mushroom valve 222, thereon. The mushroom exhaust valve 222 isoriented so that a fluid signal from point 212 is transmitted to point218, and a fluid signal from point 212 to the valve 222 prevents point218 from rapidly exhausting to atmosphere.

Point 212 of the timing circuit 202 is connected by line 224 to a firstcapacitance, such as variable volume elastomeric capacitance 226.Capacitance 226 is adapted to function in the manner of a comparablecapacitance similarly depicted in U.S. patent application Ser. No.210,653, filed Nov. 26, 1980 now U.S. Pat. No. 4,414,982 (incorporatedherein by reference) but has a considerably longer potential volume forreasons seen hereinafter. Point 224 of circuit 202 is connected by line228 of the NOR gate 204.

NOR gate 204 comprises a power stream input port 204a connected to asource 230; a control port 204b; a first output port 204c; and, a secondoutput port 204d. Line 228 is connected to the control port 204b. A line232 is connected from output port 204d to the second fluidic timingcircuit 206. NOR gate 204 is of a type that, unless a signal is appliedat port 204b to deflect output to port 204d, provides output at port204c.

Output port 204d of NOR gate 204 is connected by lines 232 and 234 to apositive pressure input terminal of a conventional pressure-to-electric(P/E) switch 236. Switch 236 is connected by an electrical line L9 toindicator means 242 which includes, for example, one or more of thefollowing: audible alarm means, visual alarm means, and counter means.

The second fluidic timing circuit 206 is essentially a fluidic one-shotcomprising a first output port 206a vented to atmosphere; a secondoutput port 206b connected via line 240 to the valve 208; a first inputport 206c connected to a source 230; a second input port 206d; and, athird input port 206e. Input port 206d is connected by line 232 tooutput port 204d of the NOR 204. The fluidic timing circuit 206 furthercomprises a substantially closed-loop fluidic path 244 which has a firstend thereof communicating with port 206d and a second end thereofcommunicating with port 206e. The fluidic path 244 has thereon one ormore timing means, such as a fluid restrictive device 246 and/or acapacitance device 248. As shown in the embodiment of FIG. 8, therestrictive device 246 is a variable resistor and the capacitance 248 isa variable capacitance, such as an elastomeric balloon. The restrictivedevice 246 and capacitance 248 can be interchanged with similarrestrictive devices or capacitances having different values andcapacitances as desired.

As mentioned above, output port 206b of the fluidic timing circuit 206is connected via line 240 to the valve means 208. Valve 208 as shown isa two-way, two position solenoid spool valve, such as an ALCON Series AModel 7986 valve. Although any suitable conventional valve may beutilized. Valve 208 has two port 208a and 208b in its bore. Valve 208 isconnected so that a positive pressure on line 240 moves the valve 208into the position shown in FIG. 8A wherein port 208a thereof isconnected to port 208b.

Port 208b of valve 208 is connected by line 250 to a point 252 on line.A fluidic resistor 254 on line 250 insures that the path of leastresistance from the cannula 48 is through the line 46 and through thevalve 26 rather than through line 250.

Port 208a of valve 208 is connected by a line 256 to a capacitance 258,which in turn is connected by line 260 to a flowmeter 262. Flowmeter 262is connected by line 264 to a pressure regulator 266. Pressure regulator266 is connected to a source 268.

The embodiment of FIG. 8B basically resembles the embodiment of FIG. 8Abut does not employ the second fluidic timing circuit 206 and the valvemeans 208. Instead, the positive pressure port of the P/E switch 236 isdirectly connected to the output port 204d of NOR 204. The electricaloutput of the P/E switch 236 is connected a electrical line L10 throughan electrical stimulator controller to a conventional electromyographicelectrode 270. Electrode 270 is positioned under the chin of a patientin close proximity to a hypoglossal nerve (the twelfth cranial nerve).

The operation of the apparatus of the embodiment of FIG. 8C basicallyresembles the operation of the embodiment of FIG. 1C. However, with thecontroller 32' of FIG. 8C, when the timer 88 of controller 32'determines that the in vivo respiratory system has not attempted afurther inspiration before the expiration of a first maximum timeinterval, timer 90 is not triggered to provide a further pulse of gas.Moreover, although a short apnea event corresponding to the firstmaximum time interval has already occurred and been indicted by LED 94and alarm circuit 100, the embodiment of FIG. 8C further functions to(1) determine when the in vivo respiratory system has failed to attempta further inspiration before the inspiration of a second maximum timeinterval (the second maximum time interval being greater than the firstmaximum time interval and indicative of a long apnea event), and (2) toprovide a high pressure pulse of gas to the in vivo respiratory systemin an attempt to dislodge any occlusion or obstruction in the upperairway passages of the in vivo respiratory system.

In the above regard, when output indicative of non-negative pressure inthe in vivo respiratory system occurs at port 30e of amplifier 30, theoutput is applied to the first fluidic timing circuit 202. The fluidicoutput signal travels around line 216 of circuit 202, closing themushroom valve 222. From thence the signal is applied to the variablecapacitance 226 on line 224. The fluid signal is continuosly applied tothe variable capacitance device 226 so long as output occurs at port 30eof amplifier 30.

In normal breathing the output of amplifier 30 will switch to port 30dlong before the variable capacitance device 226 is filled to its maximumcapacity. In this regard, it is recalled that amplifier 30 switches itsoutput from port 30e to port 30d when an inspiration is sensed. In thiscase, the patient is breathing satisfactorily and there is no apneicevent.

In abnormal breathing, however, when the patient fails to inspire,amplifier 30 continues to generate a fluid signal on output port 30e.Accordingly, the variable capacitance device 226 continues to expanduntil it is inflated to its maximum capacity. When the variablecapacitance device 226 is inflated to a pressure which expands it to itsmaximum capacity, the fluid pressure builds on line 228 and causes thepower stream entering port 204a of NOR gate 204 to switch from outputport 204c to output port 204d. In this manner, the NOR gate 204 createsa fluid signal on line 232. The fluid signal on lines 232 and 234 areconnected to the pressure/electric switch 236 which converts the fluidsignal on line 234 to an electric signal on line L9. The electric signalcan perform various diagnostic operations, such as activate anelectrocardiogram (ECG) monitor, an alarm, or a counter.

Various sizes and types of elastomeric balloons or other appropriatedevices may be chosen for the variable capacitance device 226. Factorsto be considered in making the choice of which device to use include theelastomeric tension exerted by the device and the maximum fluid-storingcapacity of the device. For example, if it were desired that the apneicevent circuit 200 indicate that the patient has not inspired within a 60second-second maximum time interval, the device 226 should be selectedso that it can accommodate the volume of fluid generated by amplifier 30for that 60 second period without triggering a switch in NOR gate 204.Of course, should the patient inspire before the variable capacitancedevice 226 reaches its maximum pressurized capacity, the device 226acting in conjunction with the mushroom valve 222 is quickly deflated inthe manner described above.

It should be evident from FIG. 8A that, absent a fluid signal on line232, the power stream entering port 206c of the circuit 206 is vented toatmosphere through output port 206a. However, when the fluid signal isapplied on line 206d, the power stream entering at port 206c isdeflected to the output port 206b for a period of time in the mannerhereinafter described.

Upon application of the fluid signal on line 232 to the port 206d of thesecond circuit 206, the power stream entering port 206c is deflectedfrom the output port 206a to the output port 206b, thereby creating afluid signal on line 240 which is applied to the valve means 208. Thefluid signal on line 232 is also applied to the fluidic path 244 whichhas thereon timing means (such as the resistance 246 and the capacitancedevice 248). The timing means delays the passage of the first fluidsignal around the closed loop fluidic path 244 for a pre-determinedtime. That is, an appropriate valve is chosen for the resistance of thevariable resistor 246 and a capacitance device 248 of appropriatemaximum capacity is chosen so that the first fluid signal travellingaround the closed loop fluidic circuit 244 will be delayed for apredetermined time before the signal reaches the port 206e of thefluidic circuit 206. When the fluid signal travelling around the closedloop fluidic path 244 reaches the port 206e, the fluidic pressure oneach side of the power stream entering at port 206c is equalized so thatthe power stream is no longer deflected out the port 206b but instead isagain vented to atmosphere through the port 206a.

The valve 208 receives a supply of gas ultimately from source 268 butcan transmit the gas only when a fluidic signal is applied on line 240in the manner described above. When a fluidic signal is applied on line240, the valve 208 is operated to connect port 208a thereof to port 208bfor a time period whose duration is determined by the duration of thesignal on line 240. As seen above, this duration of the signal on line240 is determined by the selected values associated with the resistanceand capacitance of the delay loop 244.

Valve 208 functions to provide a high pressure pulse of gas through line250 to the single hose cannula 48 in an effort to dislodge an upperairway obstruction of occlusion which may have caused the long apneaevent. In some instance the pressure supplied by the pulse should be ashigh as 50 pounds per square inch. The amplitude of the pulse iscontrollable through the various devices (regulator 266, capacitance258, flowmeter 262) shown connected intermediate valve 208 and source268.

It should be understood that various methods can be used to operate theapparatus of FIG. 8A. For example, in one mode of operation a highpressure pulse of limited duration is applied. In another embodiment thefluid circuit 206 can be adapted so that a high pressure pulse trailsoff to a continuous flow of lesser pressure. It can yet be envisionedthat a series of high pressure pulses can be applied in a programmablemanner.

The embodiment of FIG. 8B functions much in the manner of FIG. 8A but,rather than supply a high pressure pulse of gas through a valve means,uses the P/E switch 236 to generate an electrical signal on line L10 forapplication to the electrode 270. Electrode 270, positioned under thechin in close proximity to a nerve controlling a muscle or the like,such as the hypoglossal nerve for the tongue, provides stimulus for themuscle to dislodge itself from the upper airway so that the movement ofthe muscle and associated organs can again be in coordination with thediaphragm of the in vivo respiratory system.

FIG. 8C illustrates a further embodiment of the invention whichaccomplishes objectives similar to that of the embodiment of FIG. 8A.The apparatus of FIG. 8C resembles the apparatus of FIG. 6. Thecontroller 32' of FIG. 8C, however, does not have its point 104connected to the input terminal 80b of NOR 80. Rather, point 104 isconnected by line L7 to a two-position two port solenoid spool valve272. Valve 272 of FIG. 8C is connected to a source 268 in much the samemanner as valve 208 of FIG. 8A is connected to source 268.

In the operation of the embodiment of FIG. 8C, whenever controller 32'determines that an apnea event [having a duration corresponding to apredetermined yet variably selectable maximum time interval establishedby the position of switch 100] occurs, a high pressure pulse of gas issupplied through the operation of valve 272 in a manner easilyunderstood from the foregoing other embodiments.

It should be understood that sensing means 28C of the embodiment of FIG.1C may be used with any of the embodiments disclosed herein. Also, eachof the disclosed embodiments may be appropriately modified as discussedabove to operate in either a spiked pulse or a square pulse mode.Further, it should be understood by those skilled in the art that thesolenoid operated spool valves disclosed herein may be replaced withlatching solenoid valves, such as the PNeutronics Series 11 valve.

The embodiments of the invention in which an exclusive property orprivilege is claimed are defined as follows:
 1. An apparatus for sensingnegative pressure in an in vivo respiratory system and for supplying gasto said in vivo respiratory system, said apparatus comprising:valvemeans having first, second and third ports, said first port beingselectively communicable with either said second port or said thirdport; a single line connected to said first port of said valve means,said line adapted both to transmit to said valve means negative pressureindicative of an inspiration in said in vivo respiratory system and totransmit gas to said in vivo respiratory system; a source of gascommunicating with said second port of said valve means; means forsensing negative pressure in said in vivo respiratory system, saidsensing means communicating with said third port of said valve means;and, means for controlling said valve means, said control means beingresponsive to said sensing means for selectively connecting said firstport of said valve means to said second port thereof when negativepressure is sensed and for maintaining said connection for at least aportion of the time duration of said negative pressure in said in vivorespiratory system so that gas may be supplied to said in vivorespiratory system, said control means also being adapted to reconnectsaid first port of said valve means to said third port thereof after theapplication of gas to said in vivo respirating system.
 2. The apparatusof claim 1 wherein said valve means is a slideable three-way twoposition spool valve.
 3. The apparatus of claims 1 or 2 wherein saidsingle line is connected to application means for applying gas to saidin vivo respiratory system, and wherein said application means comprisesa nasal cannula.
 4. The apparatus of claim 1 wherein said sensing meanscomprises a fluidic amplifier.
 5. The apparatus of claim 1 wherein saidsensor means comprises a pressure to electric sensor.
 6. An apparatusfor sensing negative pressure in an in vivo respiratory system and forsupplying humidified gas to said in vivo respiratory system, saidapparatus comprising:valve means having first, second, third and fourthports wherein said valve means selectively communicates either saidfirst port with said third port or said second port with said fourthport; a single line connected to said first port of said valve means,said line adapted to both transmit to said valve means negative pressureindicative of an inspiration in said in vivo respiratory system and totransmit humidified gas to said in vivo respiratory system; a source ofgas communicating with said second port of said valve means; means forsensing negative pressure in said in vivo respiratory system, saidsensing means communicating with said third port of said valve means;humidifying means, said humidifying means having an input port connectedto said fourth port of said valve means and an output port connected tosaid line connecting said in vivo respiratory system to said first portof said valve means; and, means for controlling said valve means, saidcontrol means being responsive to said sensing means for selectivelyconnecting said fourth port of said valve means to said second portthereof when negative pressure is sensed and for maintaining saidconnection for at least a portion of the time duration of said negativepressure in said in vivo respiratory system so that humidified gas maybe supplied to said in vivo respiratory system, said control means alsobeing adapted to reconnect said first port of said valve means to saidthird port thereof after the application of humidified gas to said invivo respiratory system.
 7. The apparatus of claim 6 wherein saidsensing means comprises a fluidic amplifier.
 8. The apparatus of claim 6wherein said sensor means comprises a pressure to electric sensor. 9.The apparatus of claim 6 wherein said single line is connected toapplication means for applying gas to said in vivo respiratory system,and wherein said application means comprises a nasal cannula.
 10. Theapparatus of claim 6 wherein said humidifying means is a bubblehumidifier.
 11. The apparatus of claim 6 wherein said valve means is aslidable two way spool valve.